Corrosion inhibitors



United States Patent 3,523,894 CORROSION INHIBITORS Samuel E. Jolly, Ridley Park, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Filed July 18, 1966, Ser. No. 565,701 Int. Cl. C23f 11/10 U.S. Cl. 2528.55 Claims ABSTRACT OF THE DISCLOSURE This specification discloses compositions and methods for inhibiting corrosion normally caused by oil well fluids. The compositions comprise a major amount of an amine salt wherein the amine is wherein R is selected from the group consisting of aliphatic and cycloaliphatic hydrocarbon radicals having 12 to 30 carbon atoms and the acid is wherein R R R and R are selected from the group consisting of CH and H.

l Ra

wherein R R R and R are CH or H, and to processes of inhibiting corrosion in oil wells using such compositions.

Protection of metal surfaces from corrosion is an important factor in many fields of technology. One manner of providing such protection is by use of a corrosion inhibitor which forms an adsorbed protective film on a metal surface, which film resists attack of the surface by corrosive agents in fluids with which the surface would otherwise come in direct contact. The present invention provides a highly effective corrosion inhibitor for such use.

One application of corrosion inhibition which is of great importance in petroleum production is the inhibition of corrosion normally caused by oil well fluids such as mixtures of crude oil and brine. Corrosion of metal tubing, casing, pumps and other equipment used in producing oil from wells is a particularly diflicult problem in petroleum production. The mixtures of crude oil and brine which are produced in most wells are highly corrosive to the metals of which such equipment is commonly constructed, particularly when the brine contains hydrogen sulfide, carbon dioxideor other acidic materials.

3,523,894 Patented Aug. 11, 1970 Amine salts of acids have been proposed as oil well corrosion inhibitors. For example, U.S. Pat. No. 3,054,750 discloses using acids having the formula;

where R is a hydrocarbon radical having 12 to 30 carbon atoms, and n is an integer from 0 to 5. R is preferably aliphatic or cycloaliphatic. In a preferred embodiment R is the hydrocarbon residue of petroleum naphthenic acids. Also proposed by this patent are salts of these acids and N-alkyl trimethylene diamines having the formula;

where R is a hydrocarbon of 12 to 30 carbon atoms.

It has now been found that oil Well corrosion inhibitor compositions exhibiting improved properties over the compositions of Pat, No. 3,054,750 comprise the N-alkyl trimethylene diamine salts of acids having the general structure;

wherein R R R and R are CH or H. Surprisingly it has been found that these compositions exhibit improved corrosion protection over those known in the art, as will be shown infra.

The preferred salt of this invention is that of u,oc'-dl methylmuconic acid (DMMA) which can exist in three isomeric forms, cis-cis, cis-trans, and trans-trans, which can be depicted by the following structural formulas:

HsC

C=C C O OH HO O 0 C=C H CHa c1s-c1s HaC H C=C CH3 H0 0 C C= H C O OH cis-trans HO O C H HaC C=C H C 0 0H trans-trans The three isomeric dimethylmuconic acids are white 5 crystalline powders with the physical properties listed in Table I.

TABLE I Cis-cis Ois-trans Trans-trans Molecular weight 170. 2 170. 2 170.2 Melting point, C 1 223-224 1 179-180 1 332-333 Ionization constants (at 25 0.): 3 6

. 0. 244 0. 0036 2 1. 97 1 0. 032 Ethyl alcohol 22. 7 0. 39 Ethyl acetate 0. 185 2. 17 0. 39 0. 994 7. 60 0. 112 Benzene 0. 006 0. 023 0. 008

1 Melting Point varies with the rate of heating. 5 At C.

All of the acids which flt the general formula may be prepared by the method disclosed in U.S. Pat. 3,383,289,

issued May 14, 1968, which involves the fermentation of C to C methylbenzenes having 1 to 4 methyl groups to produce the corresponding unsaturated dibasic acids.

Additionally the preferred a,u'-dimethylmuconic acids may be prepared by the peracetic oxidation of p-xylenol to give the cise-cis isomer as described by Elvidge et al., J. Chem. Soc., pp. 1026 to 1033 (1952). This is inverted by boiling alkali to the trans-trans acid or isomerized by sulfuric acid to the lactonic acid which when esterified and treated with sodium methoxide gives the half methyl ester of cis-trans-a,a-dimethylmuconic acid.

The diamines useful in this invention are of the formula:

RNHCH CH CH NH wherein R is a hydrocarbon radical having 12 to 30 carbon atoms. R may be aliphatic or cycloaliphatic.

In the preparation of the amine salts, the acids and the amine are simply mixed together in the liquid or partially liquid state. Both the monoand diacid salts may be prepared according to the relative proportion of reagents used. The temperature is maintained below 100 C. in order to avoid formation of amide linkages. Amides are avoided since they give generally inferior results as corrosion inhibitors, particularly for use in preventing corrosion normally caused by oil well fluids.

The corrosion inhibiting compositions disclosed herein are particularly useful for inhibiting corrosion of metal equipment used in production and transportation of oil well fluids, including gas well fluids and gas condensate Well fluids, such corrosion being normally caused by materials such as H 5, CO and lower organic acids. The inhibitors can be commingled with the well fluids in any suitable manner, e.g. by introducing them, either alone or dissolved in a suitable solvent such as an aromatic hydrocarbon solvent, into the well tubing or into the annulus between the tubing and the casing. The salt can alternatively be incorporated in a solid stick inhibitor containing microcrystalline wax or other suitable material. The injection practices which are known for use with other organic inhibitors are generally suitable for use with the present inhibitor. Preferably, the salt is added to the corrosive well fluids in amounts of to 1000 p.p.m. based on the well fluids, e.g. a mixture of crude oil and brine. In addition to their corrosion inhibiting properties, the salts have detergency characteristics which make them useful in maintaining metal surfaces of well production equipment in clean condition, and in removing corrosion products or scale from corroded metal surfaces.

The compositions are useful in other corrosion inhibition application also, being generally useful in protecting ferrous metals, the protection being accomplished by means of a layer of the composition on the metal surface which is to be protected. Preferably, they are first dissolved amounts of the inhibitor in the solvent are those within the approximate range from 0.01 to 1.0 weight percent, though any larger amount which is soluble in the solvent can be employed. Generally the salts of this invention are less soluble in water, hydrocarbons, alcohols, etc. than those disclosed in Pat. 3,054,750. This is advantageous because they are not as rapidly depleted by the well fluids when used as inhibitors.

The inhibitors can also be employed in greases comprising gelled hydrocarbon oils as described in the U.S. Pat. No. 2,736,658 previously cited. Preferred amounts of the inhibitor in the grease are those within the approximate range from 1 to 5 weight percent though any larger amount which is compatible with the grease can also be employed.

The following examples illustrate the invention.

EXAMPLES I and H Salts of N-tallow trimethylene diamines with a,a-dimethyl-cis,cis-muconic acid were prepared. The diamines employed were a material known by the trademark Duomeen T and comprised a mixture of diamines hav ing the formula RNHCH CH CH NH where R is a hydrocarbon radical derived from tallow, the average molec ular weight of the mixture of diamines being 320. Since the mixture of diamines is not pure, the combining weight of Duomeen T is about 400.

Mono-salts were prepared by admixing the diamines with the theoretical amount of acid required to neutralize one amino group of the diamines with one carboxyl group. Disalts were also prepared by using twice that ratio of the acid.

These salts were then tested as corrosion inhibitors for oil well fluids according to the following procedure: Approximately equal volumes of a severely corrosive kerosene saturated with hydrogen sulfide, and of brine containing 13.24 grams per liter of CaCl -2H O, 3.5 g./l. of Na SO 6O g./l. of NaCl, 10.68 g./l. of MgCl -6H O, 1.0 g./l. of Na CO and 400 to 600 p.p.m of H 8 were placed in a bottle, together with amounts of the amine salt mixture as indicated in Table II, expressed as parts per million based on the sum of the volumes of oil and brine A cleaned and weighed /s" rod of mild steel was placed in the bottle, and the latter was sealed. The liquids nearly filled the bottle, the remaining fluid being largely air. The bottle was placed on the periphery of a drum which was rotated at a rate of about 100 revolutions per minute for a period of 24 hours. The test was carried out at room temperature. The steel rod was then removed, cleaned, and weighed to determine the weight loss from corrosion by the oil and brine. This weight loss was compared with that obtained in a blank run with no inhibitor, and the percent reduction in weight loss by use of the inhibitor and the percent protection determined. The percent protection results are given in Table II, Columns A and B.

TABLE II.SALTS A B C D Diamlne RNHCHzCHzCHzNHz RNHCHzCHzCHzNHz RNHCHzCHzCHzNHg RNHOH CH OH NH and Cis, on DMMA Cis, e15 DMMA N-naphthenyl alanines N-naphth enyl aniline; Mole ratio acid to diamina 1:1 2:1 1:1 2:1

Parts per million: Percent protection in a protective hydrocarbon oil or other suitable solvent, and the solution is applied to the surface. Suitable operation in the latter instance is disclosed for different inhibitors in US. Pat. No. 2,736,658, and similar operation can be employed in the present instance. Preferred The table further shows the results obtained with the compositions prepared in Example III of US. Pat. No.

3,054,750 (indicated as C and D in Table II). Although the salts of this invention do not exhibit extraordinary film life, a comparison of results in the Table does indicate that not only do the compositions of the present invention exhibit generally greater protection at a particular concentration over the N-naphthenyl alanine salts but also, surprisingly, significantly maintain their activity at eX- tremely low concentrations. For example, at a concentration of 50 parts per million, the N-naphthenyl alanine salts exhibited percent protection of 16.0 and 73.0 while the cis, cis DMMA salts, at the same concentration showed percent protection of 85, 82, 86 and 84.

What is claimed is:

1. A method for inhibiting corrosion on ferrous surfaces normally caused by oil well fluid containing corrosive agents selected from the group consisting of hydrogen sulfide, carbon dioxide, and lower organic acids, said method comprising introducing into said oil well fluid, a salt of an amine and an acid wherein the amine has the formula RNHCH CH CH NH wherein R is selected from the group consisting of aliphatic and cycloaliphatic hydrocarbon radicals having 12 to 30 carbon atoms, and the acid has the formula R2C C 0211 Ra- /C 0211 C 1 R4 5. The process of claim 1 wherein the salt is the disalt of the acid H020 (IJ=CHCH=o C 02H CH3 CH3 References Cited UNITED STATES PATENTS 2,833,712 5/1958 Jones 2528.55 2,839,465 6/1958 Jones 2528.55 3,383,289 5/1968 Raymond et a1 19528 FOREIGN PATENTS 762,228 11/1956 Great Britain.

HERBERT B. GUYNN, Primary Examiner US. Cl. X.R. 

